Diseases of the Intestines and Nutritional Approach

9. Diseases of the Intestines and Nutritional Approach

Diarrhea in Kittens

Diarrhea in kittens is a very common consultation that can be difficult for the veterinarian to manage. It may affect a litter or a colony, or a specific kitten in an age range from two to twelve months. Digestive problems in kittens in the perinatal period and up to the age of 2 - 3 months are the subject of concern for every breeder and they expect urgent, concrete solutions from their veterinarian. A kitten with diarrhea rapidly becomes dehydrated and requires on average 14 - 16 mL of water / 100 g BW (Malandain et al., 2006).

Tube feeding kittens requires skill. Breeders should be taught by a veterinarian before attempting the procedure themselves. If the feeding tube is not positioned properly (in the trachea instead of the esophagus) milk may enter the kitten’s lungs and cause death. (©É. Malandain/UMES).

When a kitten is presented with diarrhea and its general condition is satisfactory, the two preferred hypotheses are dietary intolerance or parasitism. The prevalence of parasitic diseases in young carnivores is significant and sometimes underestimated, at both the colony and individual level (Spain et al., 2001).

The feces of kittens are usually soft and yellow. (©Brau/UMES).

When there is no mother to care for the kitten, elimination must be stimulated after each feeding. (©C. Bastide).

Digestive Disorders in Orphan Kittens

This period of life without maternal assistance is complex. Very young animals are poikilothermic, without a layer of fat. Hypothermia always results in paralytic ileus, so prevention is important. In these circumstances, the living environment requires special attention, and dietary standards need to be fulfilled.

The main causes of diarrhea in this period are:

• Over-consumption (Hoskins, 1995)
• Poorly prepared or poorly conserved milk substitute, given at the wrong temperature.

Factors affecting the successful rearing of an orphan kitten are the quality of mother’s milk and hygiene during feeding, thermal regulation, the quality of sleep, nursing, external stimuli and socialization. Constipation is quite common in the orphan kitten. In the vast majority of cases, it is linked to a lack of perineal stimulation, which stimulates the elimination of stools. For orphaned kittens, large litters and primiparous mothers, the breeder should ensure that defecation and urination is accomplished effectively. Otherwise, the transit of food through the digestive tract will be slower and will promote the reabsorption of water causing constipation to occur. The administration of paraffin oil is not recommended in the kitten. Repeated stimulation of the perineum and soft washing are preferable. In more serious cases, the veterinarian may need to anesthetize the kitten to administer an enema.

Digestive Disorders Caused by the Diet During Weaning

Physiologically, this is a critical phase for the kitten, who has an immature immune and digestive system (Figure 33), and is therefore vulnerable when placed in an environment with strong infectious and parasitic pressures. During weaning, a kitten faces several types of stress. The most important are:

• Change of diet
• Detachment from the mother
• Acclimatization to a different environment and microbism

Figure 33. Variations in the digestibility of different nutrients during kitten growth. (From Harper & Turner, 2000).

It is difficult to suggest recipe-types of weaning modalities. Every method is respectable if the results are good. Weaning begins the fourth or fifth week and most finish by week 7.

The main causes of diarrhea in this period (not including infectious and parasitic diseases) are:

• Poor digestibility of the food
• Poor conservation of the food - over-consumption at mealtimes
• Excess starch in the diet (Figure 34).

Figure 34. Development of the kitten’s carbohydrate digestion capacity before and after weaning, compared with an adult’s. (From Kienzle, 1993).  

Idiopathic Enteritis in Kittens

Kittens aged 6 - 12 months may present with diarrhea that is refractory to the usual symptomatic treatments, and yet resolves spontaneously in a few months (Hoskins, 1995). These cats present with profuse diarrhea, however, they are in good general condition. The diagnostic tests are all within normal limits. The underlying cause maybe due to improper maturation of the digestive tract’s absorption and exchange system, exacerbated by errors in dietary supervision.

In practice, weaning can start when the kittens’ average daily gain starts to decline. Weaning usually ends around the age of 7 weeks. (©Y. Lanceau/RC/British shorthair).

Diagnosis

The clinical signs are not specific to the disease. A methodical approach is necessary to consider the circumstances in which the diarrhea appears, the life context of the animal and the findings of the clinical examination.

A breeder needs to be educated about which clinical signs need to be identified early, the most concerning signs and the criteria for hospitalization. If the kitten is presented by a private individual, a full history (unrestricted access to the outside, contact with sick animals, possibilities that a toxin has been ingested, signs observed) will be needed before the clinical examination can be conducted. The seriousness of the clinical signs is correlated to the origin of the diarrhea.

The following hospitalization criteria may be employed for kittens (Battersby & Harvey, 2006):

• Alteration of the general condition (asthenia, anorexia)
• Abnormalities of cardiac rhythm: bradycardia or tachycardia
• Hyperthermia or hypothermia
• Dehydration
• Presence of blood in the feces
• Abnormal abdominal palpation (mass, lymph nodes, etc.)
• Presence of other clinical signs: frequent vomiting, icterus, etc.

In the event of hospitalization, fluid and electrolyte therapy must be implemented and the kitten placed in isolation, if necessary.

The diagnostic evaluations are adapted to each specific clinical situation and include:

• Hemato-biochemical analyses (leucocytosis, anemia, hyper- or hypoproteinemia). Exudative enteropathy is accompanied by hypoproteinemia, while hyperproteinemia is more consistent with feline infectious peritonitis (FIP). The young age of the kitten must not exclude metabolic causes of diarrhea;
• Coagulation tests in cases of digestive bleeding
• Fecal analyses (fecal cytology, bacteriology, larvae, cysts, protozoans)
• Detection of retrovirus (FeLV, FIV)
• PCR on blood and/or rectal sampling (FIV) (Figure 35)
• Measurement of fTLI, using a specific feline assay.

Figure 35. Cytobrushes used for fecal detection of viral enteritis. PCR is a laboratory technique for amplifying the genetic material of the virus and detecting its presence even at very low quantities. There are various types of applicators or cytobrushes used to collect samples for coronavirus testing (here per rectum). (©G. Casseleux/UMES).  

Treatment of Diarrhea in Kittens

A systematic approach is required for acute diarrhea of sudden onset, without alteration of the general condition. Diagnostic examinations must be conducted if the clinical signs persist for longer than a couple of days and a second round of symptomatic treatment should not be started if the first one fails, even if the clinical signs are only a week’s duration. Diarrhea is not considered to be chronic until it enters its third or fourth week.

Specific treatment for each disorder must be started. Observance is a limiting factor in cats. It may be difficult for private individuals with many cats or colonies to follow the nutritional instructions. Novel protein diets can be recommended for the dietary treatment of kittens with diarrhea. Low fibre concentrations are probably the best recommendation to start unless there are indications for a large bowel problem. Other helpful supplements are probiotics, that can be helpful in the modulation of the intestinal microbiota (Guilford & Matz, 2003; Marshall Jones et al., 2006). The efficacy of prebiotics such as fructo-oligosaccharides has to be evaluated depending on the individual reaction.

Upon identification of diarrhea in a breeding colony, some practical steps should immediately be implemented: the sick kittens should be isolated, and new kittens, quarantined. Prevention also demands good hygiene and disinfection of the premises. (©Y. Lanceau/RC/British shorthair).

Infectious Gastroenteritis

The term "infectious" is employed liberally here. This section examines forms of viral, parasitic and bacterial gastroenteritis that most commonly affect cats. The exposure of the digestive tract to different pathogenic agents is not always expressed by the appearance of clinical signs (Guilford & Strombeck, 1996c). Any disturbance of the physiological mechanisms of homeostasis is however likely to generate an imbalance in the microflora or induce modifications in local antigenicity, causing diarrhea.

Viral Gastroenteritis

The prevalence of all the viruses that infect cats is unknown (Guilford & Strombeck, 1996c). These viral infections provoke highly varied clinical signs: discreet alteration of the general condition or necrosing enteritis in the event of panleukopenia. These diseases propagate themselves quickly and are highly contagious. Their prevention demands a systematic approach comprising rigorous hygiene measures, the quarantine of new individuals and vaccination wherever possible.

Feline Enteric Coronavirus

Feline coronavirus shares antigenic and morphological characteristics with the one of FIP. Today, it is commonly thought that a mutation of coronavirus can lead to the expression of FIP. Viral replication occurs in the apex of the microvilli. Infected animals develop moderate and transitory digestive problems. Sometimes there are no visible clinical signs.

Feline Infectious Peritonitis

This disease manifests in a variety of clinical forms. The most commonly described form is the presence of inflammatory effusion in the cavities. The "dry" form is characterized by granulomatous inflammation of the parenchyma (pancreas, liver, digestive wall, lymph nodes). FIP is therefore not expressed as a common chronic or acute gastroenteritis. It often affects young animals, but not exclusively so. Fever is a common sign. Laboratory evaluation (hematology, biochemistry, PCR, etc.) helps to underpin the clinical suspicion.

A last form – more specific and less well known – is atypical isolated granulomatous colitis. The modifications it produces on an ultrasound are equivocal (Harvey et al., 1996). The prognosis is invariably poor.

Viral diseases (coronavirus, feline infectious peritonitis, retroviruses, feline panleucopenia) are always likely to appear in a cattery or colony, even when hygiene conditions are good and medical prophylaxis is meticulously observed. (©G. Casseleux/UMES).

Retroviruses (FeLV – FIV)

The FeLV virus is responsible for superacute mortal enterocolitis and lymphocytic ileitis. The FIV virus is most often implicated in episodes of recurring diarrhea. Cats infected with the FIV virus may survive for long periods, during which time they will intermittently present with digestive disorders of varying intensity. Immunosuppression may favor enteric infection (Battersby & Harvey, 2006) and the diarrhea will be secondary to other infectious agents rather than to the presence of the FIV virus.

Feline Panleukopenia

Feline panleukopenia is due to a parvovirus with epidemiological, physiopathological and hematological characteristics similar to those of the canine virus (Squires, 2003). The pathogenic power of the virus is also expressed on the central nervous system in utero or during the neonatal period (cerebellar hyperplasia) (Guilford & Strombeck, 1996c).

The clinical signs manifest themselves 4 - 7 days after transmission of the virus by the fecal-oral route. The virus is very stable in the exterior environment. Viral replication occurs in tissues that rapidly multiply: bone marrow, lymphoid tissue, intestinal crypts. The jejunum and ileum are the most often affected digestive segments. Viral replication produces leukopenia and necrosis of the intestinal crypts that leads to hemorrhagic enteritis. The clinical signs are dominated by major asthenia, rapid anorexia and weight loss, vomiting and diarrhea. Death may occur before the appearance of the diarrhea in the superacute forms. Massive bacterial translocation is the cause of septic shock. Liver failure is often the cause of death.

Several other viruses cause acute digestive disorders in cats. These include astrovirus (isolated in kittens) rotavirus (which causes neonatal diarrhea), reovirus and calicivirus. Their identification is difficult and their pathogenic role has not been clearly identified.

Parasitic Gastroenteritis

Parasitic Infestations

The parasitic infestation must be extensive before clinical signs manifest themselves: bloating, vomiting, diarrhea, skin lesions, coughing during larval migration. The incidence of parasitic enteritis is higher in colonies and in young animals. It is underestimated among individual owners (Battersby & Harvey, 2006). Various infestation modes are possible: fecal-oral route, in utero contamination (toxocarosis), transmission through colostrum or milk, ingestion of intermediate hosts (tapeworms).

The location of the parasites is variable. They are often found in the small intestine, but the large intestine is also infested. The presence of these parasites may also cause anemia, melena (hookworm disease), sudden inexplicable deaths in the cattery, stunted growth or fertility problems among breeding stock.

The most commonly encountered parasites are ascarids (Figure 36 & Figure 37) (Toxocara cati, Toxascaris leonina), tapeworms (mostly Dipylidium caninum) (Figure 38), hookworms (Ancylostoma tubaeformae) and Strongyloides tumefaciens in tropical areas. The diagnosis is based on fecal evaluation (flotation in zinc sulfate).

Figure 36. Adult roundworms. Adult roundworms are long and round, measuring 4 - 10 cm. (©National Veterinary School of Alfort (ENVA)/Parasitology).

Figure 37. Roundworm egg. (©©National Veterinary School of Alfort (ENVA)/Parasitology).  

Figure 38. Segments of Dipylidium caninum. (©Royal Canin).  

The treatment of parasitic enteritis uses anthelmintics, which are available in many forms: oral pastes, small caplets adapted to cats, trans-dermal (spot on). The active substances and their spectrum of action are listed in Table 7.

Treatment of the mother is recommended two weeks prior to the birth, then during weeks 3, 5 and 7, to stop the parasitic cycle.

Protozoan Diseases

The digestive tract of cats may be colonized by protozoans: Giardia, Coccidia and Trichomonas.

Giardia

Less common in cats than dogs, giardiasis is expressed by digestive disorders that may be intermittent (diarrhea does not present a specific aspect) as well as dysorexia episodes or deterioration in the general condition. An immunosuppressive condition favors the clinical expression of giardiasis. Trophozoites are attached to the brush border of the proximal small intestine. They are periodically excreted in the feces, which is why several fecal examinations spaced over intervals of several days are desirable to avoid a false negative diagnosis. An ELISA diagnostic kit is available for practitioners.

The treatment of giardia uses imidazoles: metronidazole, fenbendazole. With resistant strains, the environment should be properly decontaminated (elimination of feces and disinfection with quaternary ammoniums). Animals must be cleaned as recontamination is possible by the ingestion of oocysts (Figure 39) deposited on the coat by licking.

Figure 39. Oocysts from Giardia Oocysts survive in humid environments and some wild animals are reservoirs of this disease. (©National Veterinary School of Alfort (ENVA)/Parasitology).  

Coccidia (Isospora felis, Isospora rivolta) (Figure 40)

This protozoan disease is common in breeding colonies and its expression is strengthened by an underlying parasitic condition and unfavorable hygiene. The clinical expression may include the following signs:

• Stunted growth in kittens
• Abdominal pain
• Fever
• Tenesmus
• Mucoid diarrhea

Hygiene on the premises is important in prevention. Treatment is based on the association of trimethoprim-sulfonamides with clindamycinor toltrazuril for resistant forms.

Figure 40. Oocysts from Isospora felis immature (top) and infectious (lower). Maturation of the oocysts requires at least 48 hours. (©Brau/UMES).  

Trichomonas (Tritrichomonas foetus, Pentatrichomonas hominis)

Trichomoniosis seems to be an under-estimated cause of recurring digestive disorders in young cats, especially in colonies. The pathogenesis of these organisms is multifactorial in interaction with the host’s endogenic flora (Gookin et al., 1999). The disease is expressed when hygiene is inadequate: diarrhea predominates with hematochezia and/or mucus, peri-anal inflammation, rectal prolapse. Transmission is directly via the fecal-oral route.

The identification of protozoans by fecal analysis is difficult. They can be easily confused with giardia. Fecal culture tests are commercially available (In Pouch TF©). Their presence in the colon is expressed by an influx of inflammatory cells (lymphoplasmocytes or neutrophilic leukocytes) and sometimes crypt abscesses (Yaeger & Gookin, 2005). Eradication is difficult, as trichomonas are resistant to imidazoles. A recent study mentions the over-representation of purebred cats, especially the Siamese and the Bengal (Gunn-Moore et al., 2007).

Bacterial Gastroenteritis

Some pathogenic bacteria may cause episodes of acute or chronic diarrhea. Unlike protozoans, their presence is clearly overestimated. Antibiotic treatment should only be started after isolation of an enteropathogenic bacterial strain. Inappropriate antibiotic treatment may provoke serious imbalances in the intestinal flora, and favor the development of bacterial antibiotic resistance.

The main pathogenic bacteria described in cats and responsible for digestive disorders include (Henroteaux, 1996):

• Campylobacter (possible healthy carrier)
• Salmonella (possible healthy carrier, septicemic risk if pathogenic)
• E. coli (enteropathogenic strains)
• Clostridium perfringens
• Yersinia enterocolitica

Clinically, bacterial diarrhea has strong repercussions on the general condition, as well as fever and the regular presence of blood in the feces. A serum electrolyte profile should be conducted to guide fluid and electrolyte rehydration and to correct the frequent hyperkalemia.

The history must probe for sick people that are in contact with the cat. The diagnosis is based on fecal cytology that indicates the presence of leucocytes and bacterial elements. The diagnosis is confirmed by bacterial culture of the feces.

Acute Gastrointestinal Diseases

Etiology

In cats, acute gastrointestinal diseases are most commonly caused by diet, parasites or toxins (see above). They are expressed by the association of vomiting and diarrhea with varying characteristics. Cats sometimes tend to defecate outside the litter box when suffering from this type of diarrhea.

Vomiting predominates in the event of occlusion.

Procedure for Diagnostic Evaluation

Diagnostic tests are rarely justified initially. Hospitalization should be proposed according to the same criteria as described for diarrhea in kittens:

• Alteration of the general condition and dehydration
• Tachycardia and bradycardia
• Fever
• Hematemesis
• Abdominal pain or abnormal palpation
• Suspicion of peritonitis

The sequence of diagnostic tests is dictated by the history and tailored to each case. It includes hematological analyses (leukopenia, leukocytosis, anemia), viral tests (FeLV, FIV), fecal analyses, radiograph and ultrasound examinations if occlusion is suspected.

Nutritional Measures

Acute vomiting and diarrhea usually mean that the patient should be fasted (nil per os [NPO]). Oral feeding is not practicable in cats if vomiting persists or diarrhea is profuse. Because of the consequences of vomiting and diarrhea for the electrolyte and acid-base balance, parenteral fluids with electrolytes and buffering substances should be administered. Oral rehydration can be administered when tolerated. If the water losses are high because of vomiting and severe diarrhea, fluid has to be administered by parenteral application. Fluid should be administered as a mandatory measure if there is evidence of dehydration (>5%) or the patient refuses to drink.

If the condition improves and the animal is willing to accept a small amount of food, frequent small meals should be administered for 24 - 72 hours depending on individual tolerance. Examples of appropriate homemade diets are boiled rice with 2 parts of boiled lean meat (chicken or turkey) or eggs. Milk and milk products such as low fat cottage cheese (low lactose content) can be used, although the high lactose concentration may be a problem. An alternative is a highly digestible commercial diet with a low-fat concentration. During the acute stage it is often recommended to use a protein source that is not part of the normal diet (sacrificial protein) to avoid sensitization or the development of allergies. The fiber content of diets for patients with acute intestinal problems has to be limited to ensure optimal tolerance and digestibility. The levels of potassium, sodium and chloride should be increased because vomiting and diarrhea induce high electrolyte losses. When clinical signs improve, the usual diet can be reintroduced gradually.

Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBD) are the main cause of chronic digestive disorders in domesticated carnivores, especially cats. The term covers a group of idiopathic diseases, while certain pathogens have been implicated in their clinical and anatomicopathological expression (food antigens, parasites, bacteria). Many studies implicate complex interactions between the patient’s particular predispositions, immunity problems related to the mucosa and the digestive microflora. Knowledge of IBD has progressed over the last fifteen years, with the advent of ultrasound and endoscopic examinations of the cat’s digestive tract.

Definition

IBD is defined in accordance with the histological criteria: infiltration of the mucosa of the small and/or large intestine by a population of inflammatory cells, most often lymphoplasmocytic (Figure 41a and Figure 41b), although neutrophilic leukocytes, eosinophilic leukocytes and macrophages may also be involved (Tams et al., 1996a).

The most restrictive definition of IBD entails the presence of lesions only in the small and/or large intestine. However, some authors do not exclude IBD in the event of inflammatory gastric lesions (Guilford, 1996). Very often in fact, intestinal lesions are not isolated and the entire digestive mucosa is affected by the influx of inflammatory cells in the lamina propria.

Figure 41a. IBD in a cat: histological examination. Increased number of intra-epithelial lymphocytes in the villus epithelium as well as increased numbers of lymphocytes in the lamina propria of the villus and the basal mucosa between the crypts. (©Valuepath, Laboratory for Veterinary Pathology, Hoensbroek, The Netherlands).

Figure 41b. IBD in a cat: histological examination. High power magnification of a villus with marked presence of intra-epithelial lymphocytes and lymphocytic infiltration of the lamina propria. (©Valuepath, Laboratory for Veterinary Pathology, Hoensbroek, The Netherlands).

Clinical Reminders

No breed or sex predisposition has been recognized and all age groups may be affected, including young adults. The intensity of the clinical signs varies greatly from animal to animal: chronic digestive disorders (diarrhea and/or vomiting), dysorexia and inconsistent alteration of the general condition. These manifestations may develop "by crises" for months or even years before becoming permanent. These diseases are better documented in cats than in dogs (Jergens, 2006). At the beginning of the disease, vomiting is predominant and may be the expression of intestinal lesions, even distal ones. The vomiting of gastric juice well after mealtime and in the morning on an "empty stomach" is common.

Diarrhea may be a sign of lesions of the small intestine (profuse, very watery diarrhea) or a colonic disorder (tenesmus, the presence of mucus or blood, minor undermining of the general condition), but this dichotomy is much less specific in cats than dogs. In other cases, episodes of constipation occur before the appearance of diarrhea.

Abdominal palpation may reveal thickening of the intestinal loops and an increase in the size of the associated lymph nodes. In other cases, abdominal palpation may be perfectly normal.

Diagnosis

The diagnosis of IBD is by exclusion of other diseases that could cause the clinical signs or an inflammatory influx into the digestive mucosa (neoplastic infiltration, bacterial proliferation syndrome, hyperthyroidism, protozoans) (Krecic, 2001).

Endoscopy is conducted after diagnostic tests for other conditions are completed (CBC, biochemical analyses, fecal examination, basal T4 measurement, abdominal ultrasound) (Simpson et al., 2001).

Abdominal Ultrasound

Abdominal ultrasound precedes endoscopy in the exploration of digestive diseases of the cat. The assessment of the parietal layers (Figure 42) and the size of the lymph nodes are essential to help eliminate the hypothesis of lymphoma. Ultrasound also confirms whether there are lesions in the pancreas, liver or bile ducts, as cats with IBD often have concurrent cholangitis.

Figure 42. 3.5 year old female Siamese cross cat, who presented with frequent vomiting. Abdominal ultrasound shows an enlargement in the parietal region. Transabdominal biopsies confirmed a diagnosis of severe eosinophilic enteritis. (©V. Freiche).  

Endoscopy

Both upper and lower gastrointestinal endoscopy is necessary to establish a precise diagnosis. A number of endoscopic biopsies must be obtained from all accessible segments:

• Upper: stomach, duodenum, proximal part of jejunum
• Lower: distal part of the ileum, colon.

The histological analysis of biopsies may involve one or more cell types. The most common inflammatory infiltrate is lymphocytic/plasmacytic. The inflammatory infiltration may be polymorphous (the presence of neutrophilic leukocytes, a varied number of eosinophilic leukocytes (Figure 43), histiocytes). Villous atrophy may also be associated with the disease (Figure 44). Its presence often worsens the prognosis.

Figure 43. Eosinophilic colitis in a cat (large intestine). Marked infiltrate of eosinophilic granulocytes as well as some plasma cells in the lamina propria between the crypts. (©VALUEPATH, Laboratory for Veterinary Pathology, Hoensbroek, The Netherlands).  

Figure 44. Chronic eosinophilic enteritis (small intestine). Villous atrophy with blunted villi, a band of fibrous tissue at the transition between villi and crypts and a moderate infiltrate of eosinophilic granulocytes. (©VALUEPATH, Laboratory for Veterinary Pathology, Hoensbroek, The Netherlands).

Visual Appearance of the Lesions

The visual appearance of the mucosa is never specific. There is poor correlation between the visual appearance and the histological score. In cats, the correlation between the clinical signs and the histological distribution of lesions is unsatisfactory. Visual classification is difficult due to certain subjective parameters that depend on both the operator and the equipment. Endoscopy produces a fairly reliable histological map. It is the fastest exploratory technique and less burdensome for the animal than exploratory laparotomy, which should only be performed in special circumstances. The nature of the inflammatory infiltrate and its distribution along the digestive tract leads to the elaboration of more specific therapeutic protocols (Strombeck & Guilford, 1991; Sturgess, 2005).

Biopsies

Associated parietal fibrosis may be suspected during biopsy (difficulty of taking biopsy fragments of normal size, resistance to traction when the forceps are closed). If this is so, additional biopsies should be performed to obtain samples of sufficient size for reliable histological analysis. This would also permit identification, in the same segment of the digestive tract, of more or less modified sections. Central needle biopsy forceps may also be useful, as they are more effective on a more rigid mucosa surface.

Management

Medical Treatment

Despite the possibility of standardized therapeutic plans, the veterinarian must consider each case as an individual entity. One of the pitfalls of treatment is the lack of observation among cat owners. Treatment comprises the administration of the substances listed below.

• Digestive flora regulators with immunomodulation properties (metronidazole) (Zoran et al., 1999).
• Sulfasalazine is tolerated less well in cats than dogs and its indications are specific and limited (see feline colitis).
• Corticosteroids are proposed in the most severe cases but large doses are not generally essential to ensure clinical stabilization, as refractory cases are uncommon. The minimal effective dose must be established to enable alternate day corticotherapy at the earliest opportunity. Long-acting corticosteroids are used for cats, but they are less effective than prednisolone administered orally.
• Other immunosuppressive agents may be proposed if there is no response to corticosteroids, depending on the histology results of biopsies. These include chlorambucil, cyclosporine and azathioprine (Zoran, 1999). Note that cats are extremely sensitive to the toxic side-effects of azathioprine and its administration requires a close monitoring and reevaluation of the treated cat.

IBD comprises by definition a group of chronic diseases that require protracted treatment. Relapses are common. It is essential to educate the owner about the disease and its management and to set realistic expectations for the care of the cat. (©M. Münster).

Dietary Treatment

Patients with inflammatory bowel disease often suffer from malnutrition (Figure 45) due to inadequate dietary intake compared to increased requirements, maldigestion and malabsorption, and excessive fecal nutrient losses.

Figure 45. Dietary treatment of IBD cases is similar to the management of dietary allergy. (©Dr Paul Mandigers).  

Exclusion diets and hydrolysed protein-based diets are often favorable in IBD cases because they can positively interact with the mucosal inflammation (Waly et al., 2006). Inflammation of the gut wall itself can impair the absorption of amino acids, peptides and carbohydrates as well as the transport of minerals and fluid. A highly digestible diet may also be beneficial. Most cats can tolerate a high-fat diet (> 20% DMB in a dry food). Some patients may do better on a low-fat diet (~ 10% DMB) because fatty acids can be hydroxylated in the gut by certain bacteria and stimulate secretory diarrhea. Probiotics and prebiotics may be used as feed additives in IBD patients, although there are no controlled clinical trials providing evidence for their efficacy in IBD cases.

Adverse Food Reactions

Food allergy, intolerance or sensitivities can be summarized under "adverse food reactions". They are often considered to be a cause of chronic gastrointestinal diseases. Commonly, they are divided into:

• Non-immunologically mediated reactions
• Immunologically mediated reactions, synonymous to "food allergy" (German & Zentek, 2006).

Clinical signs may affect the gastrointestinal tract or other organs or systems. Dermatological signs are most common in the event of gastrointestinal problems.

Etiologies

In many cases clinical gastrointestinal signs are caused by food intolerance that is not based on immunological mechanisms. True allergies are difficult to assess in practice and may be less important than commonly assumed. The main compounds in commercial diets that may cause dietary allergy or adverse reactions are protein sources. In principal, all commonly used proteins such as beef, pork, vegetable proteins, and fish have to be considered as potentially problematic.

Diagnosis

The diagnosis is mainly based on dietary history and clinical investigation. This procedure is subjected to individual influences and the frequency of an "allergy" as a diagnosis is dependent on the investigator.

In all patients that are suspected to have a dietary intolerance, a complete overview of the dietary history of the patient is mandatory, including information on the usual diet, treats or table scraps. In some cases, problematic food compounds can be identified, which is essential for formulating an elimination diet or selecting adequate diets from a commercial source. When it is not possible to identify the offending compound, the choice of an initial elimination diet depends on the history of ingredients used in the individual’s diet.

Specific assays for the characterization of adverse reactions to food are not yet available, so first diagnosis is mostly made on the observation that the disease responds to dietary changes (Hall, 2002). The gold standard of diagnosis involves the response to the exclusion diet and the subsequent challenge with provocation test (Allenspach & Roosje, 2004). A specific diagnosis based on indirect blood allergy tests is questionable and may produce erroneous results.

Common test diets for cats are based on lamb, chicken, rabbit or venison, often in combination with rice or green peas. An improvement in clinical signs is suggestive of food allergy or at least an adverse reaction to food ingredients (Wills & Harvey, 1994). The diagnosis should be confirmed by reverting to the original diet. The development of clinical signs can be expected immediately or within one or two weeks of feeding. Therefore, a trial length of 2 - 3 weeks would appear appropriate in most GI cases. Food provocation trials can be performed to identify the ingredient causing the problem, adding single protein sources sequentially for 7 days at a time. Most owners will not pursue this if the elimination diet has worked successfully. In conclusion, diagnosis requires dietary elimination-challenge trials and clinical signs; routine clinico-pathological data, serum antigen-specific IgE assay, gastroscopic food sensitivity testing, or gastrointestinal biopsy can only be supportive (Guilford et al., 2001).

Dietary Treatment

Dietary management of adverse reactions to food follows the same principles as discussed for diagnostic procedures. Unfortunately, the practitioner is dependent on the compliance of the owner. This may become critical, as clinical signs can respond slowly or relapse. Dietary protocols should follow a standard concept. In the long run, a balanced diet composition, high digestibility in the small intestine and a restricted number of ingredients are important (German & Zentek, 2006). This facilitates the digestive process, limits the antigenic load in the gut and supports the absorption of nutrients.

Type of Diets

Home-prepared diets have a place in the treatment of cats with dietary indiscretions, although commercial diets with limited number of ingredients are often preferred because of the higher safety in application and the greater convenience. Diets with hydrolysed proteins offer an interesting alternative for the treatment of cats with a dietary allergy that is not responsive to "normal" antigen restricted diets.

Dietary Change

A dietary change can be helpful regardless of the etiology and can contribute to a better outcome in many cases. A "new" diet may have a beneficial impact on the intestinal digestive processes and it may also influence the composition and metabolic activity of the gut bacteria. A dietary change may limit the growth of undesirable microorganisms and so reduce concentrations of microbial metabolites in the gut. Microbial metabolites like the biogenic amine histamine can have a negative impact on the health of cats.

Once a diet has been selected, it has to be fed as the sole source of food for at least 12 weeks to determine whether the desired response will occur. GI signs will often resolve sooner than dermatological signs.

Protein Sources

The choice of the best-suited dietary protein is the key to the outcome of the case.

• Lamb has commonly been used, but the widespread use of ovine protein in pet food may make this choice less promising.
• Fish is less suitable for cats because many commercial cat foods are fish-based or have fish as a minor ingredient. Fish can be a common cause of adverse food reactions in this species (Guilford et al., 2001).
• Wheat (and barley, oats) gluten can cause dietary allergy and celiac disease in humans. Their use is probably also critical in cats, which suggests the need to change the carbohydrate source in all cases with suspected food allergy.

Fat sources may also contain small amounts of protein from the basic animal or plant raw material. Although these traces of protein appear to be of minor importance, they could theoritically affect the result of an elimination trial but this potential influence is strongly debated.

Hydrolysed protein sources are often used in commercially available veterinary diets. Protein is treated enzymatically to alter its structure. They are split by enzymatic treatment into small peptides. The enzymatically released peptides are less likely to interact with the immune system due to their low molecular weight. The high digestibility of these diets may be advantageous in patients with gastrointestinal disorders.

Carbohydrate Sources

Generally, a single source of carbohydrate is recommended to avoid misinterpretation. Maize, potatoes, rice, green peas, and tapioca may be suitable.

Minerals, Trace Elements and Vitamins

Minerals and trace elements have to be added to make a diet complete and balanced. However, some sources of mineral salt, like bone meal, contain small amounts of protein, which may itself provoke an adverse reaction.

Supplementation of home-prepared diets with vitamins can also be problematic, since some of the commonly used vitamins are protected by encapsulation with gelatin (usually prepared from pork). Although the production process is strict and most potentially antigenic epitopes are destroyed, traces of proteins or peptides may still be introduced into a diet. One option is to use a home-prepared diet, based on a minimum of dietary ingredients. Adult cats will tolerate this for some weeks without developing severe nutrient deficiencies. However, home-prepared diets need to be balanced and complete if they are fed long-term or nutrient deficiencies will develop.

Medical treatment is based on the therapeutic plans implemented for IBD.

Diseases of the Colon

Megacolon

Progressive local or total distension of the colon and the loss of motility lead to fecal retention which is characterized by chronic constipation and aggravates over time. Cats are affected more commonly than dogs.

Physiological Reminders

The proximal colon plays an important role in the absorption of water and electrolytes from the luminal content. The mucosal parietal cells actively absorb chloride (Cl-) and sodium (Na+) ions by ATP dependent pumps. This mechanism results in passive water absorption.

The distal colon permits the storage and periodical elimination of feces. If peristalsis of the colon is passive (the parasympathetic nervous system generates peristaltic contractions, while the sympathetic nervous system regulates segmentary contractions), defecation is a willful act, under the control of the central nervous system. The colonic transit time is variable in carnivores (forty hours or so).

The longitudinal and circular muscle walls are responsible for motility and colon tone. This motility is regulated by gastrointestinal hormones and intrinsic and extrinsic innervation of the colon. There are movements that mix the contents of the colon (rhythmic segmentary contractions) and retrograde contraction waves in cats (Figure 46).

The anaerobic colonic flora participates in a number of reactions: the liberation of medications, and the production of endogenous compounds (volatile fatty acids).

Figure 46. Types of contraction observed in the colon.

Etiopathogenesis

Congenital megacolon is described in the Siamese. It is said to be due to the absence of ganglion cells in the myenteric and submucosa plexus (aganglionosis).

The acquired forms result from organic lesions (anatomical lesions of the pelvis, neoplasia and intraluminal stricture), metabolic abnormalities (hyperkalemia), neurological disorders (dysautonomia) or are of undetermined origins (idiopathic megacolon, which accounts for around 62% of cases according to Washabau (2003)).

Clinical Expression

Owners report chronic constipation in cats, associated with vomiting. Painful abdominal palpation is evidence of a highly distended, colon that is hardened throughout its length. A rectal swab without sedative will enable elimination of the cause of distal obstruction and deformations of the pelvic canal.

Low occlusion is observed and demands hospitalization of infused animals (renal biochemical values are often high). The fecalith is evacuated under anesthesia, by colostomy in the most severe cases.

Diagnosis

Radiograph examination suffices to establish the diagnosis (Figure 47). An examination of the front of the pelvis is necessary to exclude any old trauma that may have caused modification of the pelvic canal.

Endoscopy is not useful in establishing a diagnosis, unless an endoluminal lesion is suspected that has caused dilatation proximally in the colon.

Figure 47. Megacolon in a cat who previously suffered from pelvic fractures. (©V. Freiche).  

Medical Treatment

Medical treatment is exclusively palliative. Its success is closely linked to the motivation and availability of the owner, as recurrence is immediate without continuous nursing. In the medium term, surgery or euthanasia may be justified by the owner’s lack of motivation.

• Prokinetics: Cisapride was the drug of choice for treating megacolon, however, it is not available in every country.
• Laxatives: Lactulose (0.2 mg/kg 3 times per day per os) or appetent medicinal oil sometimes delays the need for surgery. Rectal laxatives empty the rectal ampulla but do not have any effect on transit. Enemas are often poorly tolerated by the animal and are irritating in the medium term.

Dietary Treatment of Constipation

Many cats with constipation respond positively to an increased fiber level, but the physical and chemical properties of fiber sources differ considerably so they should be selected according to the desired effect.

In practice, it may be necessary to adjust the amount of fiber according to patient tolerance and the clinical effects. In cases of severe problems due to constipation or fecal impaction, the laxative effects of soluble fibrous sources (e.g., psyllium) are used specifically for treatment. Fermentable carbohydrates like lactulose or lactose may be recommended in constipated cats (Meyer, 1992). The dosage needs to be adjusted on a case by case basis to ensure the patient produces a slightly moist stool with increased acidity. The fecal pH will be around 6.5 when adequate amounts of lactulose are ingested. Liver, milk and milk products are diet ingredients with mild laxative properties.

Insoluble Fiber

The gut flora ferments dietary fiber sources with low solubility slowly or not at all. Cellulose is a good example of a dietary fiber source with low degradability by intestinal bacterial fermentative processes. It increases the bulk in the large intestine and the increased gut fill helps stimulate intestinal motility. Depending on the structure and chemical composition, some insoluble fiber sources can trap water (Robertson & Eastwood, 1981). The concentration of insoluble fiber should be limited, as insoluble ingredients tend to lower the digestibility of the diet.

Soluble Fiber

Typical examples of soluble fiber sources include beet pulp, psyllium, pectin from carrots or fruits, and gum such as guar gum. Soluble fiber has a higher water-holding capacity than insoluble fiber due to its gel-forming capacity (Robertson & Eastwood, 1981; Rosado & Diaz, 1995).

Soluble fiber is generally easily fermented by intestinal bacteria (except psyllium). The fermentation processes induced by the ingestion of fermentable fiber have a strong impact on the colonic milieu, because bacteria release organic acids as metabolism products that tend to reduce the colonic pH. The SCFA produced by bacteria can be utilized as energy yielding substrates by the colonic mucosa. Butyric acid has beneficial effects on the integrity and function of the gut wall and organic acids may also have some regulatory effects on motility.

Negative effects of higher amounts of soluble dietary fiber include an excessive production of SCFA and a risk of osmotic diarrhea.

Colitis

Colonic diarrhea is the result of failure of the colon’s water and electrolyte reabsorption function, which determines the water-content of feces. The colon’s reabsorption capacity (colonic reserve) can in fact be saturated. It is the proximal part of the colon that is responsible for this regulatory function.

Inflammatory colonopathies are a group of diseases whose pathophysiology is still largely unknown. Some factors have been clearly identified (e.g., parasitic or bacterial causes), but the origin of the colonization of the colonic mucosa by inflammatory cell populations of different histology types remains obscure. The factors involved are highly varied. They include immune-related, medication (NSAID), diet, hereditary (breed colonopathies) and even behavioral factors. In many cases, the pathogenesis proposed in humans is not transposable to domestic carnivores.

Clinical Signs

Most colorectal diseases are clinically expressed by diarrhea or constipation. However, it is uncommon for these clinical expressions to provide information on the etiology of the colon.

The owner of a cat often has difficulty gaining insight in the defecation habits of the animal. Diarrhea is suspected when the cat defecates outside the litter box or in the event of soiled hair around the anus. Diarrhea of the large intestine is generally characterized as follows:

• preserved general condition (except advanced neoplasia)
• Frequent emission of soft stools, of normal or increased volume, in a pile, the consistency of which changes in the course of the day (gradual softening)
• Regular presence of mucus or blood
• Observation of tenesmus, anal pruritus.

In cats, flatulence and vomiting complete the clinical signs.

Diagnosis

The anamnesis provides essential pointers, which sometimes provide information on the duration of the disease’s development and whether the diarrhea is acute or chronic, permanent or intermittent. Recurring diarrhea is considered to be chronic.
Abdominal palpation must be done very carefully: thickening of part or the entire colon, hyperplasia of the associated lymph nodes, abnormal rigidity, and abnormal content in one or more segments.
A rectal swab is difficult to perform on cats without sedation.

Complementary Examinations

A parasitic fecal examination should always be performed ahead of any more complex examinations of the colon, even if the animal has been properly dewormed. Evaluation using a fecal float is desirable. Parasites and protozoans most frequently implicated in this location are hookworms (Uncinaria stenocephala) and some protozoans: mainly giardia, coccidia.
Fecal Culture: few cases of colitis are caused by bacteria (Campylobacter, Clostridia, Yersinia). The identification of Escherichia coli or Candida albicans colonies rarely has pathological significance.
Hematological and biochemical examinations are part of the differential diagnosis (e.g., metabolic diseases), but few changes are observed specifically in terms of inflammatory colonopathies (peripheral eosinophilia in case of parasitism or feline hypereosinophilic syndrome).
Radiography: without contrast agent will generally not reveal most parietal colonic diseases, except if the lesions are very large. If an endoluminal mass is suspected, barium contrast studies of the colon should be performed. However, this examination has largely been superseded by ultrasound and endoscopy.
Abdominal Ultrasound: the presence of air in the colon adversely affects the quality of the examination. Ultrasound of the colon may be proposed if the animal cannot be anesthetized or the differential diagnosis has been established between an inflammatory lesion and a neoplastic lesion. The presence of abnormal echogenicity or architectural modifications to the colon wall will reveal whether a lesion is isolated or diffuse, or whether there is a parietal tumor.
Coloscopy: Endoscopy is the diagnostic technique of choice when exploring colonic diseases (Figure 48). Endoscopic biopsies are essential. They provide information on the type of cell infiltrate, the treatment and a precise prognosis.

Figure 48. Normal ileal papilla identified during coloscopy in the cat. Needle biopsies in the distal segment of the ileus are essential. (©V. Freiche).  

The following visual abnormalities of inflammatory origin maybe observed during colonoscopy:

• Congestion and edema of the mucosa
• Thickening of the colonic folds
• Heterogeneous coloration of the surface of the mucosa: presence of areas of hyperemia, areas of mottled coloration
• Dilatation of the parietal glands: grayish punctuations spread across a segment of the colon surface
• Abnormal friability of the mucosa as the endoscope passes through
• Changes to the surface of the mucosa: presence of more proliferative areas (Figure 49).

Figure 49. Colonoscopy performed on an 11-year-old male Persian. The colonoscopy reveals an irregularity of the surface of the mucosa in the form of small micronodular bands. This is a case of chronic colitis. (©V. Freiche).  

Classification of Inflammatory Colitis

Lymphoplasmocytic colitis (idiopathic chronic colitis)
This is the most common type. The visual signs include the above changes. In cats, they are among the more general clinical signs of IBD.

Eosinophilic Colitis
This may be a component of eosinophilia. Eosinophilic cells often predominant in colitis, but they are always associated with a population of lymphocytes, plasmocytes and possibly neutrophilic leukocytes. Hypersensitivity reactions are implicated in the pathogenesis.

Suppurated Colitis
This is a relatively rare type, especially in cats. The clinical signs are often acute, sometimes accompanied by superinfected mucoid feces (pus traces). Ulcerative lesions are often associated with it, as are crypt abscesses. The predominant cell population are neutrophils.

Granulomatous Colitis
This is considered to be an atypical and rare form of IBD. The segmentary lesions are observed on part of the small intestine and various parts of the large intestine. These lesions have a proliferative aspect and may sometimes lead to massive thickening of the colon wall, producing stenosis. Clinically, diarrhea is profuse, generally hemorrhagic and contains a lot of mucus. An alteration of the general condition is observed.

Medical Treatment of Inflammatory Colitis

Where possible, the treatment should be etiological if the cause can be identified (parasitic, bacterial, viral colitis) (Zoran, 1999).

Use of Antibiotics
The prescription of antibiotics must be limited to highly precise indications and respond to reasonable use. The clinical and hematological criteria may impose the use of certain wide-spectrum substances of low toxicity.

A regulator effect of metronidazole on the digestive flora in domesticated carnivores has been shown during colonopathies. Metronidazole also has an immunomodulator activity.

Benefit of Anti-inflammatory Substances
Sulfasalazine is an anti-inflammatory agent with an active substance that is cleaved and released in the colon (5-amino salicylic acid). It regulates local prostaglandin production and reduces the influx of leukocytes.
In cats, the recommended dose is either 10 mg/kg BID or 15 mg/kg SID. Several therapeutic plans are available of varying length. Sulfapyridine, which is released into the colon when the substance is cleaved, is responsible for known side effects: hematological disruptions, skin rashes, hepatic lesions, Sjögren’s syndrome. Cats maybe more sensitive to the side-effects of sulfasalazine compared to dogs.

Corticosteroids and Immunosuppressors
Corticosteroids are an indispensable part of the treatment of a number of chronic inflammatory colonopathies. A medium-size dose has an anti-inflammatory action (inhibition of prostaglandins and antileukotriene effect), while higher doses have an immunosuppressive effect.

Oral administration is preferred to the parenteral route. Cats tolerate corticosteroids better than dogs. They can be administered in a higher dose in the induction phase. The dose should be adapted on the basis of the clinical response.

In the most serious cases or when corticosteroid therapy is contraindicated, additional immunosuppressive treatment may be proposed. Several weeks will be needed to judge effectiveness; and there are many side effects (particularly medullary toxicity) and constraining clinical and hematological checks will be necessary.

Topical Agents and Dressings
These are adjuvant substances that provide local protection. Some animals are less likely to be effected a second time if a clay bandage (smectite or zeolithe) is used in the medium term. Zeolite, or sodium silicoaluminate, a tetrahedral clay, is capable of adsorbing bacterial toxins, bile acids, and gases. By forming a protective film over the intestinal mucosa, zeolite helps enhance the intestinal mucosal barrier. Compliance is a limiting factor.

Dietary Treatment

Although colitis is most frequently diagnosed in dogs, it is becoming increasingly common in cats (Simpson, 1998). Colitis can be beneficially influenced by adequate dietary treatment in cats, although this depends on whether it has mainly an infectious, inflammatory or immune-mediated pathogenesis (Zentek, 2004).

Importance of High-quality Protein
Unlike fats and well-cooked starches, which are almost totally digested in the small intestine, the digestibility of proteins varies according to source and treatment. The ingestion of low-quality proteins – which therefore are also characterized by poor ileal digestibility – leads to an inflow of indigestible protein matter in the colon. Greater putrefaction of proteins leads to an increase in bacterial biomass and a high secretion of water in the colon – simultaneous phenomena that result in poor stool consistency. High protein putrefaction can disrupt the colonic microflora and orient its profile towards potentially pathogenic strains (Zentek et al., 1998). The many aromatic compounds produced (mercaptan, indole, skatole etc) can have a toxic effect on the colonic mucosa in combination with the biogenic amines formed (cadaverin, putrescine, etc) and encourage cancers of the colon and rectum (MacFarlane & Cummings, 1991). The high production of ammonia may ultimately affect DNA synthesis, damage the morphology of the colonocytes and shorten their lifespan (Visek, 1978).

A good selection of proteins and a controlled manufacturing process makes it possible to considerably improve their digestibility, which is essential to good digestive tolerance in cats. Many cats that suffer from chronic diarrhea as a consequence of colonic inflammation will respond to a novel protein elimination diet or a hydrolysed protein-based diet (Nelson et al., 1984; Guilford & Matz, 2003).

Dietary Fiber
A hypoallergenic diet can be combined with a fermentable fiber source, such as pectin or guar gum. The addition of fermentable dietary fiber regulates the composition of the colonic microbiota and may reduce the potentially harmful flora.

Soluble fiber is highly fermentable and as such it plays a very important role in the ecosystem of the large intestine. It first acts as a substrate for the bacterial biomass, which provides it with the necessary energy for good growth. The resulting fermentative activity also generates a large quantity of SCFA and lactic acid. Such fermentation products (mainly SCFA) have an extremely important trophic role in maintaining the colonic mucosa in good health. Colon cell atrophy is observed in the complete absence of soluble fiber in food (Wong & Gibson, 2003).

Insoluble fiber (cellulose, hemicelluloses, lignin) is not generally decomposed to any great degree by microflora in the colon, which means they remain virtually intact in the stools. Their high hygroscopic capacity (they can absorb up to 25 times their weight) together with their ability to increase the indigestible residuum of feces help improve fecal consistency but also increase the volume of stools (Sunvold et al., 1995a).

On the other hand, bearing in mind their high fermentability, an excessive quantity of soluble fiber in food is detrimental to good digestive tolerance. The resulting high moisture content, poor consistency and high volume of stools would appear to be explained mainly by a high proliferation of the bacterial biomass (Sunvold et al., 1995a) (Table 8).

Energy Consumption

Cats with enterocolitis often have severe weight loss and anorexia leading to a cachexic body condition (Hart et al., 1994). Therefore, the careful adjustment of energy and nutrient intake is a mandatory part of successful dietary management for these patients. The palatability of a food is another very important criterion, as the nutritional treatment is recommended for several months and boredom should be avoided.

Small and Large Intestinal Neoplasia

Small intestinal tumors account for 73% of all intestinal tumors in cats (52% adenocarcinomas, 21% lymphomas). Conversely, colonic tumors are uncommon (10 - 15% of intestinal tumors in cats) (Estrada et al., 1998). The slow appearance of non-specific clinical signs rules out early detection.

Feline intestinal tumors have a better prognosis than esophageal or gastric tumors.

Small Intestinal Tumors

Different Histological Types Encountered

The two predominant types of tumor are adenocarcinomas (Kosovsky et al., 1998) and lymphomas. While most cats that present with intestinal lymphoma are FeLV negative, the former presence of the virus is implicated in the neoplastic transformation (Barr et al., 1995).

Other tumors are less common: leiomyomas, leiomyosarcomas, fibrosarcomas. Benign tumors of the duodenum, of the adenomatous polyp type have been described in cats (Estrada et al., 1998; Freiche et al., 2005b), especially oriental males without known viral impairment by FIV or FeLV.

Mastocytomas exclusively found in the digestive tract are reported in dogs. Some cases have been described in cats, in the colon of aging animals (Slawienski et al., 1997).

Carcinoid tumors (neuroendocrine) are very uncommon. Their clinical expression is generally dominated by the paraneoplastic syndrome (Guilford & Strombeck, 1996d).

Relatively undifferentiated mesenchymatous tumors in the intestines are described in cats. Biopsies of mesenchymatous lesions may require specific stains and immunolabeling.

Epidemiology

Breed and sex predispositions have been recognized. In cats, the Siamese is commonly implicated, particularly with carcinoma. Generally speaking, the incidence of intestinal lymphomas appears to be higher in males than females. Whatever the nature of the tumor, affected cats are generally at least 10 or 11 years old, although intestinal lymphomas may be identified in much younger cats. Adenomas are less common in the small intestine and are probably under diagnosed.

Clinical Signs

The alteration of the wall of the small intestine may lead to digestive transit or nutrient absorption disorders that have clinical consequences and are responsible for signs of the disease. These signs are not very specific: diarrhea, vomiting, melena. Again, they are shared with other gastrointestinal diseases, which means the etiological diagnosis is sometimes made too late.

The clinical expression of small intestinal neoplasia is linked to the location of the lesion in the intestinal wall:

• The more proximal, the more frequent vomiting will be. Melena is a relatively reliable sign, but inconsistent;
• More distal tumors are expressed by diarrheal episodes that worsen over time. The diarrhea is then characteristic of chronic small intestinal diarrhea. The overall condition of the cat is generally altered, with the presence of weight loss, dysorexia and lethargy.

In some much less common cases, the animal presents with occlusion. General loss of body condition is more visible in later stages of development. Weight loss is a sign. Feline intestinal tumors are sometimes very distal (small-large intestine junction) and are expressed in several forms (isolated, multicentric, diffuse). However, in a large proportion of cases, abdominal palpation does not identify a mass, although diffuse or segmentary thickening of the intestinal loops is often suspected.

Diagnosis

The diagnosis is obtained by traditional techniques.

• Hematobiochemical analyses provide few pointers. The differential diagnosis must exclude the metabolic causes of chronic diarrhea. Anemia is an important sign to remember (possible in the event of a lymphoma), but many intestinal neoplasias do not produce blood loss on the CBC. However, intestinal mastocytomas do cause mucosal ulcerations that may result in chronic blood loss.
• Radiography may be proposed if no other means of investigation is possible (Figure 50). The association of abdominal ultrasound and endoscopy is greatly preferable to a barium study, which is both difficult to perform and to interpret.
• Abdominal ultrasound is certainly the investigation of choice when good equipment is available. Precise signs are described for intestinal neoplasia, based on the same types of changes cited for a gastric lesion. These include modification to the parietal layers with localized or diffuse identification faults, variations in echogenicity (hypoechogenicity), abnormal satellite lymph nodes and localized peristaltic problems (Penninck, 1998; Hittmair et al., 2001).
• Endoscopy and histological analysis of biopsies are proposed when the lesion is accessible (proximal and distal small intestine). They are recommended when an abdominal ultrasound has excluded the presence of an isolated lesion of the small intestine. The histological analysis of endoscopic biopsies obtained from several locations can lead to the diagnosis. This examination has two limitations:
  - Isolated lesions of the middle of the small intestine are topographically inaccessible
  - Isolated tumor cells under the mucosa or the muscles maybe missed.
• Laparoscopy permits a beneficial approach, but it demands more sophisticated equipment.
• Trans-parietal biopsies can be performed during an exploratory laparotomy if the above examinations are not possible.

Figure 50. Colonoscopy performed on an 11-year-old male Persian. The colonoscopy reveals an irregularity of the surface of the mucosa in the form of small micronodular bands. This is a case of chronic colitis. (©V. Freiche).  

Disease Staging

Different types of examination are available to stage the disease: radiology (thoracic imaging), abdominal ultrasound and tomodensitometric examination. These complementary examinations should be used selectively, depending on the case. Metastasis is initially most often regional. Abdominal ultrasound can identify a satellite and/or regional lymphadenopathy, as well as parenchymatous metastasis, while also facilitating fine needle aspiration for an immediate diagnostic approach. The thoracic radiographs can be used to exclude the presence of pulmonary metastasis. The pulmonary tomodensitometric examination is more precise.

In cats, it may be difficult to differentiate intestinal lymphoma in its diffuse form with severe IBD. The visual aspect of the lesions are similar. When there is no logical correlation between the histological analysis of biopsies and the clinical condition of the animal, the diagnosis must be questioned, because diffuse inflammatory lesions of the digestive tract (often lymphoplasmocytic in nature) are almost always associated with feline gastrointestinal lymphoma.

Treatment and Prognosis

Therapy depends on several factors:

• The animal’s general condition and whether medical resuscitation is necessary
• The histopathological nature of the tumor: benign or malignant, risk of metastasis or local recurrence, hematopoietic status
• Local and remote disease staging

When indicated, diffuse hematopoietic intestinal tumors (lymphoma, mastocytoma), will be treated medically (Lanore, 2002). The medical treatment protocols are similar to those for lymphoma and systemic mastocytoma. They vary according to histological type.

Generally speaking, in the event of surgical treatment certain rules need to be observed (Slawienski et al., 1997):

• Eliminate all tumor cells and include ganglionic excision when possible
• Avoid dissemination of neoplastic cells, locally or remotely.

The enterectomy techniques used on healthy tissue are employed, by means of laparotomy for the different segments of the small intestine.

Colon Neoplasia

Different Histological Types Encountered

Tumors of the colon are uncommon in cats. The carcinoma is the most common histological type. It affects aging animals and males more than females. Rectal tumors are more common than colonic tumors.

The isolated colonic form of lymphoma in cats is not common, although it dominates the incidence of carcinomas in this location. In this species, the ileocolic location must always be examined (lymphoma, carcinoma, mastocytoma).

Benign isolated polyps are less common in domesticated carnivores than in humans. They do not appear to particularly precede the appearance of carcinomas, at least not through the same mechanism as in humans.

Clinical Signs

All but two of the clinical signs are non-specific. The presence of blood in feces of normal consistency and the presence of abnormally small stools are specific signs. Other clinical signs are identical to those traditionally observed during diarrhea of the large intestine (tenesmus, hematochezia, mucus etc.) (Jergens & Willard, 2000).

A rectal swab under anesthesia is necessary, as a large proportion of colon lesions caused by a tumor are located in the last few centimeters of the mucosa. There are few benefits to abdominal palpation (the lesions are not always highly exophytic or indurated).

These neoplastic processes may develop slowly and the diagnosis is made in the later stages as described with gastric carcinoma. The alteration of the general state is slow and inconsistent. The deep infiltrative and/or stenosing forms are more pronounced. Tenesmus and pain are generally less marked, except carcinomas located at the colorectal junction, where infiltration is low. The presence of ascites is uncommon at the time of diagnosis.

Diagnostic Evaluation

Coloscopy is the diagnostic technique of choice (Figure 51 & Figure 52). It does not demand any specific preparation in cats, as the feline colon is short. The administration of a diet without residue exclusively based on white meat or fish without added fiber or fat for the four days prior to the examination, followed by enemas under anesthesia, is sufficient and not very restricting.

Figure 51. Coloscopy in an 8-year-old domestic shorthair cat who presented for defecation disorders and hematochezia. The examination shows a parietal endoluminal mass which is consistent with a non-pedunculated tumor. The histological nature of the tumor cannot be determined during the examination. (©V. Freiche).  

Figure 52. 16 year old female cat who presented with constipation and marked depression. Coloscopy shows endoluminal stenosis, which is responsible for distal occlusion. The distal colic stenosis had a post-inflammatory origin. (©V. Freiche).  

Coloscopy is a tool to address part of the disease staging process and to identify whether there is one or more lesions. Colon neoplasia can present several forms: pedunculated, diffuse, in "graps" or scattered along the colonic wall: it is then difficult to macroscopically predict the histological nature of a colorectal mass. Multiple endoscopic biopsy samples must be obtained.

Disease Staging

Abdominal ultrasound is complementary to coloscopy. It allows evaluation of the regional extension of the tumor process, and must be conducted as soon as possible. Liver and lung metastases are seldom observed during the diagnosis.

Treatment and Prognosis

Surgery is the treatment of choice for localized malignant tumors. Palliative surgery may extend the animal’s life. In the event of carcinoma, the location of the lesion justifies different surgical approaches, the follow-up of which may be difficult to manage.

Radiation therapy is an excellent complementary treatment to the surgical excision of localized distal recto-colic carcinomas.
The administration of corticosteroids alone, without a chemotherapeutic protocol improves or maintains appetite while reducing the cat’s inflammation and pain. Local topical drugs such as anti-inflammatory steroids recommended for humans are not particularly beneficial in cats.

Dietary Treatment

Dietary treatment is limited to adjusting the diet composition according to the patient’s needs. A higher energy density may be efficiently provided by a higher fat diet. Long chain n-3 fatty acids from fish oil have been shown to be beneficial in different models of neoplastic disorders. Therefore, diets with a higher protein concentration, specifically a balanced spectrum of amino acids (arginine) and higher levels of micronutrients (zinc, antioxidant vitamins) may be favorable in these patients. For further information, refer to Chapter 11.

Conclusion

Dietary treatment with adequate medication is the key to successful treatment of gastrointestinal disorders in cats. Depending on the suspected disease, the choice is between highly digestible diets in the case of small intestinal and pancreatic diseases, antigen-reduced diets in the case of dietary sensitivity or allergy, and high-fiber diets when the colon is specifically affected or motility disorders occur. In practice, dietary treatment has to be adjusted individually. The response of the patient is not always predictable and good compliance is needed for optimal success.